Fundamentals of SQL - Basics with example - 15

          OBJECT VIEWS WITH REFERENCES

To implement the objects and the ref constraints to the existing tables, what we can do? Simply drop the both tables and recreate with objects and ref constrains.

But you can achieve this with out dropping the tables and without losing the data by creating object views with references.

Ex:

     a) Create the following tables

          SQL> Create table student1(no number(2) primary key,name varchar(2),marks

                  number(3));

          SQL> Create table student2(no number(2) primary key,hno number(3),city

                  varchar(10),id number(2),foreign Key(id) references student1(no));

     b) Insert the records into both tables

          SQL> insert into student1(1,’a’,100);

          SQL> insert into student1(2,’b’,200);

          SQL> insert into student2(11,111,’hyd’,1);

          SQL> insert into student2(12,222,’bang’,2);

          SQL> insert into student2(13,333,’bombay’,1);

     c) Create the type

         SQL> create or replace type stud as object(no number(2),name varchar(2),marks

                 number(3));/

     d) Generating OIDs

          SQL> Create or replace view student1_ov of stud with object identifier(or id) (no) as

                  Select * from Student1;

     e) Generating references

          SQL> Create or replace view student2_ov as select no,hno,city,

                  make_ref(student1_ov,id) id from Student2;

     d) Query the following

          SQL> select *from student1_ov;

          SQL> select ref(s) from student1_ov s;

          SQL> select values(s) from student1_ov;

          SQ> select *from student2_ov;

          SQL> select deref(s.id) from student2_ov s;

PARTITIONS

A single logical table can be split into a number of physically separate pieces based on ranges of key values. Each of the parts of the table is called a partition.

A non-partitioned table can not be partitioned later.

TYPES

1     Range partitions

2     List partitions

3     Hash partitions

4     Sub partitions

ADVANTAGES

1     Reducing downtime for scheduled maintenance, which allows maintenance operations to be carried out on selected partitions while other partitions are available to users.

2     Reducing downtime due to data failure, failure of a particular partition will no way affect other partitions.

3     Partition independence allows for concurrent use of the various partitions for various purposes.

ADVANTAGES OF PARTITIONS BY STORING THEM IN DIFFERENT TABLESPACES

1     Reduces the possibility of data corruption in multiple partitions.

2     Back up and recovery of each partition can be done independently.

DISADVANTAGES

1     Partitioned tables cannot contain any columns with long or long raw datatypes, LOB types or object types.

RANGE PARTITIONS

a) Creating range partitioned table

     SQL> Create table student(no number(2),name varchar(2)) partition by range(no)

             (partition p1 values less than(10), partition p2 values less than(20), partition p3

             values less than(30),partition p4 values less than(maxvalue));

    ** if you are using maxvalue for the last partition, you can not add a partition.

b) Inserting records into range partitioned table

     SQL> Insert into student values(1,’a’);          -- this will go to p1

     SQL> Insert into student values(11,’b’);        -- this will go to p2

     SQL> Insert into student values(21,’c’);        -- this will go to p3

     SQL> Insert into student values(31,’d’);        -- this will go to p4

c) Retrieving records from range partitioned table

     SQL> Select *from student;

     SQL> Select *from student partition(p1);

d) Possible operations with range partitions

1     Add

2     Drop

3     Truncate

4     Rename        

5     Split

6     Move

7     Exchange

e) Adding a partition

     SQL> Alter table student add partition p5 values less than(40);

f) Dropping a partition

    SQL> Alter table student drop partition p4;

g) Renaming a partition

     SQL> Alter table student rename partition p3 to p6;

h) Truncate a partition

     SQL> Alter table student truncate partition p6;

i) Splitting a partition

    SQL> Alter table student split partition p2 at(15) into (partition p21,partition p22);

j) Exchanging a partition

    SQL> Alter table student exchange partition p1 with table student2;

k) Moving a partition

     SQL> Alter table student move partition p21 tablespace saketh_ts;

LIST PARTITIONS

a) Creating list partitioned table

     SQL> Create table student(no number(2),name varchar(2)) partition by list(no)

             (partition p1 values(1,2,3,4,5), partition p2 values(6,7,8,9,10),partition p3

             values(11,12,13,14,15), partition p4 values(16,17,18,19,20));

b) Inserting records into list partitioned table

      SQL> Insert into student values(1,’a’);         -- this will go to p1

      SQL> Insert into student values(6,’b’);         -- this will go to p2

      SQL> Insert into student values(11,’c’);       -- this will go to p3

      SQL> Insert into student values(16,’d’);       -- this will go to p4

c) Retrieving records from list partitioned table

     SQL> Select *from student;

     SQL> Select *from student partition(p1);

d) Possible operations with list partitions

8     Add

9     Drop

10  Truncate

11  Rename        

12  Move

13  Exchange

e) Adding a partition

     SQL> Alter table student add partition p5 values(21,22,23,24,25);

f) Dropping a partition

     SQL> Alter table student drop partition p4;

g) Renaming a partition

     SQL> Alter table student rename partition p3 to p6;

h) Truncate a partition

     SQL> Alter table student truncate partition p6;

i) Exchanging a partition

    SQL> Alter table student exchange partition p1 with table student2;

j) Moving a partition

    SQL> Alter table student move partition p2 tablespace saketh_ts;

HASH PARTITIONS

a) Creating hash partitioned table

     SQL> Create table student(no number(2),name varchar(2)) partition by hash(no)

             partitions 5;

     Here oracle automatically gives partition names like

                                    SYS_P1

                                    SYS_P2

                                    SYS_P3

                                    SYS_P4

                                    SYS_P5

b) Inserting records into hash partitioned table

     it will insert the records based on hash function calculated by taking the partition key

     SQL> Insert into student values(1,’a’);         

     SQL> Insert into student values(6,’b’);         

     SQL> Insert into student values(11,’c’);       

     SQL> Insert into student values(16,’d’);       

c) Retrieving records from hash partitioned table

     SQL> Select *from student;

     SQL> Select *from student partition(sys_p1);

d) Possible operations with hash partitions

14  Add

15  Truncate

16  Rename        

17  Move

18  Exchange

e) Adding a partition

     SQL> Alter table student add partition p6 ;

f) Renaming a partition

    SQL> Alter table student rename partition p6 to p7;

g) Truncate a partition

     SQL> Alter table student truncate partition p7;

h) Exchanging a partition

     SQL> Alter table student exchange partition sys_p1 with table student2;

i) Moving a partition

    SQL> Alter table student move partition sys_p2 tablespace saketh_ts;

SUB-PARTITIONS WITH RANGE AND HASH

Subpartitions clause is used by hash only. We can not create subpartitions with list and hash partitions.

a) Creating subpartitioned table

     SQL> Create table student(no number(2),name varchar(2),marks number(3))

             Partition by range(no) subpartition by hash(name) subpartitions 3

             (Partition p1 values less than(10),partition p2 values less than(20));

    

This will create two partitions p1 and p2 with three subpartitions for each partition

                        P1 –   SYS_SUBP1

                                    SYS_SUBP2

                                    SYS_SUBP3

                        P2 –   SYS_SUBP4

                                    SYS_SUBP5

                                    SYS_SUBP6

     ** if you are using maxvalue for the last partition, you can not add a partition.

b) Inserting records into subpartitioned table

     SQL> Insert into student values(1,’a’);          -- this will go to p1

     SQL> Insert into student values(11,’b’);        -- this will go to p2

c) Retrieving records from subpartitioned table

     SQL> Select *from student;

     SQL> Select *from student partition(p1);

     SQL> Select *from student subpartition(sys_subp1);

d) Possible operations with subpartitions

19  Add

20  Drop

21  Truncate

22  Rename        

23  Split

e) Adding a partition

     SQL> Alter table student add partition p3 values less than(30);

f) Dropping a partition

     SQL> Alter table student drop partition p3;

g) Renaming a partition

     SQL> Alter table student rename partition p2 to p3;

h) Truncate a partition

     SQL> Alter table student truncate partition p1;

i) Splitting a partition

     SQL> Alter table student split partition p3 at(15) into (partition p31,partition p32);

DATA MODEL

2     ALL_IND_PARTITIONS     

3     ALL_IND_SUBPARTITIONS  

4     ALL_TAB_PARTITIONS     

5     ALL_TAB_SUBPARTITIONS  

6     DBA_IND_PARTITIONS     

7     DBA_IND_SUBPARTITIONS  

8     DBA_TAB_PARTITIONS     

9     DBA_TAB_SUBPARTITIONS  

10  USER_IND_PARTITIONS    

11  USER_IND_SUBPARTITIONS 

12  USER_TAB_PARTITIONS    

13  USER_TAB_SUBPARTITIONS